The purpose of this study is to test the hypothesis that increased brain serotonergic activity will result in less ventilatory variability, as seen in obstructive sleep apnea (OSA) during sleep. Since serotonergic agonist improve OSA in some patients, we are studying the effects of these agents on the dynamic nature of ventilation variability by the pseudorandom binary CO2 stimulation test before and after 5- hydroxytryptophan (5-HTP, serotonin precursor) and fluoxetine (serotonin agonist).